For class A audio,with a pentode, you do not need a step down transformer of 2.66 or 5 to 1 to each half of the secondary. You don't need push- pull, and it is OK to use cathode bias which can never be used for class B. Zero Bias Class B triode operation is to save current while idle and take a big peak for a little while. Class A is a power waster, that is why the majority of later car radios used a single Class A Transistor. The cars had bigger batteries and alternators. Ditto the 6V6, 6AQ5, 6K6 output stages. Notice that all the old communications receiver that used the single ended Class A stage called for 10 percent distortion, Ugh!
----- Original Message ----- From: <[EMAIL PROTECTED]> To: "Discussion of AM Radio" <[email protected]> Sent: Tuesday, October 04, 2005 5:21 AM Subject: Re: [AMRadio] Minature Mobile Transmitter > On 3 Oct 2005 at 0:39, Bob Bruhns wrote: > > > That's amazing. Can't argue with success. And > > the 7.5W-300V-16K p-p adds up. The published > > 12AX7 plate dissipation spec must be overly > > conservative, and the cathode must be pretty > > efficient. > > > > I always thought of the12AX7 as an audio preamp > > tube. > > It is... There HAS to be a good reason why manufacturers > used things like 6AQ5 and 6BM8 for 4 watt audio output > stages instead of a 6C4 or 12AX7 !! > > > ______________________________________________________________ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:[email protected] > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami >
